


Coming of age

by Lady_Kit



Category: Undertale (Video Game)
Genre: Body Horror, Horror, Horror as metaphore, IT IS MEANT TO BE DISTURBING, Lots of weird world-building, Nightmare Fuel, Non-consensual themes, Other, Sufficiently bizarre to qualify as an AU, THIS IS HORROR FICTION, You Have Been Warned, if you want to think of it that way
Language: English
Status: Completed
Published: 2017-10-31
Updated: 2017-10-31
Packaged: 2019-01-27 04:12:40
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,857
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12573428
Author URL: https://archiveofourown.org/users/Lady_Kit/pseuds/Lady_Kit
Summary: "S-s-so Undyne?""Yeah?""Y-you're a f-f-fish monster, right?""...""So, w-why don't y-y-you...? I mean. W-why do you l-l-live o-on land?"---The transition from childhood to adulthood is never easy...but it is particularly difficult for members of Undyne's subspecies.





	Coming of age

**Author's Note:**

> PLEASE READ THE TRIGGER WARNING IF THERE ARE THEMES IN FICTION YOU HAVE TROUBLE DEALING WITH.
> 
> Seriously, this is a HORROR story. It is intended to disturb. With that said, the trigger warning does contain spoilers. So, you decide if you would rather go in blind, or if you need to prepare yourself.
> 
> (I think I'm building this up to be more horrifying than it actually is, but I really just don't want to upset anyone who didn't come here to be upset.)

Undyne swam happily alongside her mother, the water growing colder and darker as they swam deeper and deeper. She wriggled her earfins, releasing a cocktail of pheromones to communicate her excitement—as if the little twirls and rolls she occasionally performed didn’t make it obvious enough. Her mother grinned and ran webbed fingers through the sensory tendrils atop Undyne’s skull, causing the flesh beneath to prickle. The tendrils curled around her mother’s fingers, picking up the pride that leaked from her scales.

Swirls of cyan magic rippled ahead of them, the only source of light in the dark water. Undyne spun through the water, diving deeper and deeper, chasing those ribbons of magic. The darkness closed around them. She summoned her own magic, stretching it into a ribbon that shimmered and twisted through the water. Smaller fish—non-sapient fish—darted close, attracted to the ribbon, and she snapped at them, delighted to watch them scatter but even more delighted when she caught one in her razor-like teeth. She bit down, satisfied by the crack of bone and the slide of scales on her tongue as she swallowed.

It was a good day. A _great_ day. The _best_ day! After today, she wouldn’t be a _guppy_ anymore; she’d be an adult! A full-grown monster! (Even if, technically speaking, she still had quite a bit of growing to do, but that didn’t count!) Undyne couldn’t wait. She arced through the water until she was amongst the others of her kind. Pheromones of welcome and greeting immediately answered hers, and she basked in it, adoring the attention. Today was all about her, and she couldn’t be happier if she tried.

Soon enough, her mother appeared as well, perhaps a tad embarrassed by her progeny’s eagerness, but still proud nonetheless. Together, they approached the elder clanleader. First her mother, then Undyne, flipped onto their backs and allowed themselves to go limp in a display of submission and respect. The elder lightly ruffled the mother’s sensory tendrils, giving the other female a chance to taste the intent seeping from her. Undyne’s mother was flipped upright again, then the elder cast her eyes on the smaller female.

Undyne shivered under the clanleader’s scrutiny, excited and…a little afraid. Only a _little_ , though. Even if the clanleader was, honestly, rather frightening. She stayed down in the depths, so her scales had grown pale and her eyes had filmed over. Her sensory tendrils were long and wild, wisps of cyan magic floating along their lengths. She carded her fingers through Undyne’s tendrils, careful to curl her claws inward so as not to harm the sensitive feelers.

Still shivering a little, Undyne sensed pride and welcome and…sorrow? on the old woman’s hands. The sorrow was sobering, though Undyne tried to shake it off. Those wild tendrils drifted loosely around her, touching and searching along her scales. She tried not to squirm, knowing it was rude. Patiently—or, at least, as patiently as she could—she waited for the clanleader to finish her examination, trying to ignore the rising tide of anxiety.

The hands that closed over her wrists did nothing to ease her nervousness. She tugged experimentally, wondering if she could break free if she wanted to, but the fingers only grew tighter. Her heart started to beat faster and harder. The tendrils atop her head twisted and coiled, reacting automatically to the fear chemicals her body was starting to produce. The clanleader attempted to soothe her, running her hands down Undyne’s face and pressing her thumbs into the sensitive skin behind her earfins.

Undyne tried to stay still, tried to put on a brave face when her tendrils picked up on her mother’s reassurance. Other members of her clan were reaching out as well. Some sought to restrain her more thoroughly. Most offered gentle touches, trying to reassure. Undyne forced herself to relax, noticing the sudden influx of unfamiliar pheromones. She knew all the members of her clan, or so she thought, so where were they coming from? Her sensory tendrils reached out, tasting the water, trying to determine where the newcomer was and what their intentions might be.

She did not notice her body starting to grow heavy, or how difficult it became to string thoughts together until it was too late. Even worse, she could sense her own body starting to produce pheromones in response. The clanleader’s approval drifting off her in waves, and reassurance rose from the other women of her clan. Undyne’s body heaved and twisted as she tried to fight off the effects of the foreign pheromones, but it was useless. As the source of the strange pheromones grew closer, her body grew heavier and heavier, until she was hanging limp. Helpless. Defenseless.

She weakly kicked her legs, but her body started to sink. Before she dropped into the darkness—far from the welcoming magic of her clan—her mother caught her hand and traced a glyph on her palm. ‘Strength.’ Weakly, she grabbed at her mother, desperately trying to force her fingers to work.

‘?!!’ She sketched the glyph for alarm and confusion on her mother’s arm, hoping she would understand despite Undyne’s shaking fingers—and the strange mix of pheromones her body was putting out. Welcome and acceptance…and something else, something she wasn’t entirely familiar with…did not mix easily with fear. It had to be a sickening mix to her clanmates.

Her mother briefly ran her fingers through Undyne’s tendrils, letting her sense the pride and sorrow and…a trace of fear in her mother’s pheromone signature. On her forehead, she traced the sign for ‘Womanhood’, then she released her daughter and allowed her to drop into the darkness. Her other clanmembers started fell away, leaving her to drift alone and defenseless in open water.

Body limp and dense with developing muscle, Undyne sank like a stone, and the foreign pheromones grew stronger and stronger. Against her will, Undyne’s muscles relaxed and her eyelids slitted over the protective membrane covering her eyes. She blinked, trying to think past the fog clouding her thoughts. Then something was sliding through her sensory tendrils, and she shuddered, not sure if it was in fear or pleasure. The touch wasn’t bad, in itself…but it was unwanted.

Worse, the pheromones had grown unbearably strong. They overwhelmed her thought processes until her body felt entirely out of her control. Her soul had grown hot, and her sensory tendrils felt slick, almost oily. A small creature—it felt like a fish, but she could sense its soul, so she knew it was really a monster—rolled and tunneled through her tendrils, causing sparks of cyan magic to crackle along the tips. She exhaled hard, her gills flexing. Then the other monster hovered before her eyes. It… _he_ , she realized, was small and eel-like, his humanoid torso merging seamlessly into a finned lower half. Thin sensory threads drifted off of him, each thread lit by beads of cyan magic.

Though she had never see another monster like him, her soul resonated with his, and she knew in an instant that this was a male of her sub-species. She’d never seen one before, had thought them extinct or simply…unnecessary. None of the women of her clan seemed to need or want any males, and the absence had never bothered her. It had seemed so inconsequential. Until now.

He smiled at her, revealing a set of long, needle-like teeth. The pheromones that drifted off of him were all _WELCOME! HAPPY! JOY! NEED! WANT!_ and they made her dizzy. She shook her head, features lit by the magic around them. He tilted his head slightly, looking somewhat sad, but that didn’t stop him from pressing close, touching a small hand to her chest. Her body contorted, rocked by the intent he put forth. _No!_ He ignored her rejection, digging tiny claws into her scales. His thread-like sensory tendrils landed on her skin, and the beads of magic jolted through her like an electric shock. _No…_.

Her protests grew weaker, overtaken by his intent and his pheromones and her own body’s betrayal. Her soul manifested, the faint grey light already threaded through with the green-blue glow of her magic. He released his grip on her chest and reached up, his body dwarfed by her soul. By now, she could not protest, even as his claws dug into the sides of her soul and his thin tail coiled around it. Her traitorous soul lit up, leaking magic. She could sense how that pleased him, and she closed her eyes, hoping that he would crush her soul and simply end this torture.

Instead, he stroked along the contours, his sharp fingers painless only because he didn’t seem to _want_ to hurt her. (But he was. He was hurting her in ways he didn’t seem to comprehend.) Every touch made her soul grow brighter, and made her hate herself—and him—all the more. Then, as she could sense something building within her, he leaned close and burrowed _into_ her soul. Her body seized and her mouth opened in a silent scream, though she felt no pain at the intrusion, only an unwanted, sickening kind of pleasure.

When her muscles were no longer twitching with aftershocks, she looked up at her soul, and a pit opened up in her stomach. He was lodged _inside_ of it. As she watched, his sensory tendrils, previously lying flat against his body, lifted and burrowed into the flesh of her soul. The effect of his pheromones was wearing off, and she reached for it, but as soon as it was resting between her hands, she realized that the only way she’d ever be able to extract him was to tear open her own soul. She stared at it for a long time, trembling as she tried to process what had just happened. Eventually, her soul began to ache from being manifested for so long, and she had to release it, hoping that might possibly dislodge him. Instead, both he and her soul disappeared, returning to her core together. She gulped down water, her gills flexing to expel it, and she wrapped her arms around her torso. Trying to hold herself together.

That’s how her mother found her, hours later. She drifted down beside her daughter, running gentle fingers through Undyne’s sensory tendrils. Rather than leaning into the touch, Undyne jerked away and glared at the other woman. Chin lifted and earfins flared, aggression bleeding off her and causing her mother’s tendrils to lie flat, Undyne grabbed her mother’s arm and stabbed the glyph for ‘What!?’ and ‘Why!?’ into her hand. Her mother reached for her, but Undyne pushed her away, not willing to offer her forgiveness.

The older woman held out her hand, and Undyne, still glaring, laid her own down, waiting for an explanation. ‘Family,’ was the first glyph, rapidly followed by, ‘Soul,’ ‘Bond,’ and ‘Children’. Undyne stared at her, slowly shaking her head. Smiling sadly, her mother manifested her own soul.

Floating at its center was another smaller, brighter soul. Tiny bones surrounded it; the only physical remnant of Undyne’s father.

**Author's Note:**

> Triggers for: Body horror. Heavy non-consensual themes. Unwilling restrain, both physical and chemical. Non-consensual soul-sex between underaged characters. (It is not sexualized or romanticized.)
> 
> If I missed any triggers, let me know. I tried to catch them all.
> 
>  
> 
> So, if anyone wants to know the inspiration for this little bit of nightmare fuel, go check out the mating habits of anglerfish.


End file.
